[R] how to delete some columns from a matrix based on some other indicator variable

Ya-Hsiu Chuang amichuang at hotmail.com
Wed Sep 20 22:09:05 CEST 2006


I am not very familiar with R and need help in deleting a few columns in a 

Suppose I have a indicator variable called r and it's defined as r = (0, 0, 
1, 1). A matrix D is a 3X4 matrix. If I want a new matrix which contains 
only the columns of D corresponding to the elements of r that equal to 1. 
how can i write a loop which creat a new matrix that contains only the last 
2 columns of D in this case? thanks

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